In recent years, LCD devices have been widely used as a display unit of information apparatuses such as a notebook type personal computer (PC), a word processor and the like, and video apparatuses such as a portable television, a camcorder, a car-navigation system and the like. Those apparatuses require a display unit to be lightweight, have a slim body and have a low power consumption, and the LCD device meets these requirements. Many of the LCD devices are equipped with a lighting unit therein to realize a bright screen, where the lighting unit radiates behind the display.
There are two types of lighting units depending on a position of the light source, i.e. an edge-light type and a back-light type. In the edge-light type lighting unit, a light-conductive-panel is placed behind the LCD, and a line-light-source such as a fluorescent lamp is disposed at edges of the light conductive-panel. In the back-light type lighting unit, light sources are disposed just behind the LCD. The back-light type produces rather higher brightness but is not good for a slim housing, on the other hand, the edge-light type is good for a slim housing and has more uniform brightness on a light emitting-face but cannot produce high brightness.
The edge-light type lighting unit of LCD device has been preferred for a notebook type PC because of its thinner body. The edge-light type lighting unit has been also preferred for a camcorder and a car-navigation system, where the edge-type lighting units are equipped with a plurality of fluorescent lamps, an L-shaped lamp, or U-shaped lamp, in order to keep both the advantages, i.e. thinner body and high brightness.
FIG. 6 and FIG. 7 illustrate a conventional edge-light type lighting unit employing an L-shaped fluorescent lamp.
In FIGS. 6 and 7, this lighting unit comprises the following elements:
(a) a transparent light conductive panel 51 for transmitting light; PA1 (b) an L-shaped fluorescent lamp 52 disposed adjacent to two sides out of four sides of a panel 51; PA1 (c) reflecting film 54 for leading the light illuminated by the lamp 52 to an incident face 53 of the panel 51; PA1 (d) a reflector sheet 55 disposed behind the panel 51 and reflecting the light going outside from a rear face of the panel 51 to inside the panel 51, thereby increasing illuminating light to be emitted from an outgoing face; and PA1 (e) a diffusion panel 56 disposed on the front face (outgoing face) for increasing the uniformity of outgoing light. PA1 (a) a fluorescent lamp having an L-shaped corner or U-shaped corners and disposed close to end faces of an incident face of alight-conductive-panel; and PA1 (b) a housing for holding the light-conductive-panel and the lamp. The lamp is placed at a space between the panel and a side wall of the housing.
In addition to those elements discussed above, there are still other elements such as: lead wires 58 connected to both electrodes 57 of lamp 52 for supplying a voltage from outside; a power supply such as an inverter (not shown) generating high frequency alternating current, and the power supply being wired to respective lead wires 58 via other lead wires 59 connected to the lead wires 58 by soldering; rubber holders 60 made of an insulating material such as rubber and formed in a cylindrical tube, holders 60 provided to cover exposed sections of respective lead wires 58 and 59 to secure safety because driving the lamp 52 generally requires a high voltage.
The light conductive panel 51, the lamp 52 and other elements are held by a housing 61 so that the lighting unit is formed. The lamp 52 is disposed at a space 62 between the panel 51 and a side wall 70 of the housing 61. At the same space 62, the lead wires 59 are disposed for supplying a voltage to the lamp 52.
A rear face cover 64 is disposed on the rear side of the housing 61 so that the panel 51 and the lamp 52 and others are secured and protected from outside.
However, the lighting unit constructed as discussed above has the following problems.
When the L-shaped fluorescent lamp 52 and lead-wires 59 are placed at the space 62 between the light conductive panel 51 and the side wall 70 of the housing 61, enough allowance is preferably provided at space 62. Because of the deviation of a curved-corner section 63 of the lamp 52 (approx. .+-.1.degree.) and dimensional deviations of other components must be taken into consideration, otherwise the lamp 52 or the lead-wires 59 cannot be placed at the space 62. If the lamp 52 and lead-wires 59 are tightly placed at the space 62 without enough room in the width direction, these elements will touch the housing 61 or the light conductive panel 51, i.e., the heaviest element in the lighting unit and close to a rigid body, when the lighting unit is subjected to vibration or shock from the outside. As a result, the lamp 52 is damaged, or lead-wires 59 are cut due to the shock. Further, the space 62 must have enough width secured in addition to an effective emission area 500, whereby the dimensions of the entire lighting unit become larger.